Input device with force sensing

ABSTRACT

Devices and methods are provided that facilitate improved input device performance. The devices and methods utilize a first substrate with proximity sensor electrodes and at least a first force sensor electrode disposed on the first substrate. A second substrate is physically coupled to the first substrate, where the second substrate comprises a spring feature and an electrode component. The electrode component at least partially overlaps the first force sensor electrode to define a variable capacitance between the first force sensor electrode and the electrode component. The spring feature is configured to facilitate deflection of the electrode component relative to the first force sensor electrode to change the variable capacitance. A measure of the variable capacitance may be calculated and used to determine force information regarding the force biasing the input device.

PRIORITY DATA

This application claims priority of U.S. Provisional Patent ApplicationSer. No. 61/551,346, which was filed on Oct. 25, 2011, and isincorporated herein by reference.

FIELD OF THE INVENTION

This invention generally relates to electronic devices, and morespecifically relates to input devices, such as proximity sensor devicesand force sensor devices.

BACKGROUND OF THE INVENTION

Proximity sensor devices (also commonly called touch sensor devices) arewidely used in a variety of electronic systems. A proximity sensordevice typically includes a sensing region, often demarked by a surface,in which input objects can be detected. Example input objects includefingers, styli, and the like. The proximity sensor device can utilizeone or more sensors based on capacitive, resistive, inductive, optical,acoustic and/or other technology. Further, the proximity sensor devicemay determine the presence, location and/or motion of a single inputobject in the sensing region, or of multiple input objectssimultaneously in the sensor region.

The proximity sensor device can be used to enable control of anassociated electronic system. For example, proximity sensor devices areoften used as input devices for larger computing systems, including:notebook computers and desktop computers. Proximity sensor devices arealso often used in smaller systems, including: handheld systems such aspersonal digital assistants (PDAs), remote controls, and communicationsystems such as wireless telephones and text messaging systems.Increasingly, proximity sensor devices are used in media systems, suchas CD, DVD, MP3, video or other media recorders or players. Theproximity sensor device can be integral or peripheral to the computingsystem with which it interacts.

In the past, some proximity sensors have been implemented withadditional ability to detect and determine force applied to a surface ofthe sensor. For example, by making an estimation of applied force bymeasuring the increased capacitance that is the result of the increasedcontact area when a finger is pressed against the surface.Unfortunately, some implementations of these proximity sensors have hadlimited accuracy when estimating applied force using these techniques.Because of questionable accuracy, such sensors have typically hadlimited ability to use such determined force as a basis for determininguser input. This limits the flexibility of the proximity sensor deviceto function as an input device. Thus, there exists a need forimprovements in proximity sensor device, and in particular, the abilityof proximity sensor devices to determine and respond to indications ofapplied force.

Other desirable features and characteristics will become apparent fromthe subsequent detailed description and the appended claims, taken inconjunction with the accompanying drawings and the foregoing technicalfield and background.

BRIEF SUMMARY OF THE INVENTION

Devices and methods are provided that facilitate improved input deviceperformance. The devices and methods utilize a first substrate withproximity sensor electrodes and at least a first force sensor electrodedisposed on the first substrate. A second substrate is physicallycoupled to the first substrate, where the second substrate comprises aspring feature and an electrode component. The electrode component atleast partially overlaps the first force sensor electrode to define avariable capacitance between the first force sensor electrode and theelectrode component. The spring feature is configured to facilitatedeflection of the electrode component relative to the first force sensorelectrode to change the variable capacitance. A measure of the variablecapacitance may be calculated and used to determine force informationregarding the force biasing the input device.

In another embodiment the devices and methods utilize a transmitterforce sensor electrode and receiver force sensor electrode disposed on afirst substrate. The electrode component overlaps at least a portion ofthe transmitter force sensor electrode and the receiver force sensorelectrode to define a variable capacitance between the transmitter forcesensor electrode and the receiver force sensor electrode that changeswith the deflection of the electrode component.

In some embodiments the second substrate comprises a conductive layerthat is patterned to define the spring feature and the electrodecomponent. In other embodiments the conductive layer may be furtherpatterned to define an attachment component used to couple to a casing.

In some embodiments a processing system is communicatively coupled tothe first force sensor electrode and is configured to determine acapacitance value of the variable capacitance and to determine forceinformation from the capacitance value. In other embodiments theprocessing system is further communicatively coupled to the proximitysensor electrodes and is configured to determine positional informationfor objects that are in a sensing region using the proximity sensorelectrodes. These implementations offer potential advantages of sharingcomponents between the proximity sensor and the force sensor in theinput device. Stated another way, these implementations allow forcesensing to be added to a proximity sensor with relatively low additionalcost and complexity.

In another embodiment a method of forming an input device is providedthat comprises providing a first substrate and disposing a plurality ofsensor electrodes and a first force sensor on the first substrate. Asecond substrate is patterned to define a spring feature and anelectrode component, where the spring feature is configured tofacilitate deflection of the electrode component. The second substrateis physically coupled to the first substrate such that the electrodecomponent at least partially overlaps the first force sensor electrodeto define a variable capacitance between the first force sensorelectrode and the electrode component. When so coupled, the deflectionof the electrode component feature relative to the first force sensorelectrode changes the variable capacitance. A measure of the variablecapacitance may be calculated and used to determine force informationregarding the force biasing the input device.

In another embodiment an input device is provided that comprises aplurality of proximity sensor electrodes, a transmitter force sensorelectrode and a receiver force sensor electrode disposed on a substrate.A conductive layer is patterned to define at least one attachmentcomponent, at least one spring feature and at least one electrodecomponent. The patterned conductive layer is physically coupled to thefirst substrate such that the electrode component at least partiallyoverlaps the transmitter force sensor electrode and the receiver forcesensor electrode to define a variable capacitance between thetransmitter force sensor electrode, the receiver force sensor electrodeand the electrode component. The spring feature is configured tofacilitate deflection of the electrode component relative to thetransmitter force sensor electrode and the receiver force sensorelectrode to change the variable capacitance. A casing is provided thatcomprises a mating element and a force transmission element. The matingelement is configured to be coupled to the attachment component of theconductive layer. The mating element and the force transmission elementare dimensioned such that the force transmission element applies preloadforce to the electrode component when the attachment element is coupledto the attachment component and such that the force transmission elementtransmits additional force to electrode component in response to forceapplied by a user.

Thus, the various embodiments provide improved input device performanceby facilitating the determination of force information for one or moreinput objects.

BRIEF DESCRIPTION OF DRAWINGS

The preferred exemplary embodiment of the present invention willhereinafter be described in conjunction with the appended drawings,where like designations denote like elements, and:

FIGS. 1A-C are a cross-sectional side view and partial top views of aninput device in accordance with an embodiment of the invention;

FIGS. 2A-B are a cross-sectional side view and a partial top view of aninput device in accordance with an embodiment of the invention;

FIGS. 3-6 are top views of a patterned second substrate in accordancewith embodiments of the invention;

FIG. 7 is a block diagram of a input device in accordance withembodiments of the invention; and

FIG. 8 is a cross-sectional side view of input devices in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

Devices and methods are provided that facilitate improved input deviceperformance. Turning now to FIGS. 1A-1C, cross-sectional and partial topviews of an input device 100 is illustrated. The input device 100includes a first substrate 102 with proximity sensor electrodes 104 andat least a first force sensor electrode 106 disposed on the firstsubstrate. A second substrate 110 is physically coupled to the firstsubstrate 102, where the second substrate comprises at least one springfeature 112 and at least one electrode component 114. The electrodecomponent 114 at least partially overlaps the first force sensorelectrode 106 to define a variable capacitance between the first forcesensor electrode 106 and the electrode component. The spring feature 112is configured to facilitate deflection of the electrode component 114relative to the first force sensor electrode 106 to change the variablecapacitance. A measure of the variable capacitance may be calculated andused to determine force information regarding the force biasing theinput device.

In the illustrated embodiment the input device 100 also includes aspacing layer 130, where the spacing layer 130 is pattered to define anopening 132 such that the spacing layer 130 does not overlap at least aportion of the electrode component 114 and to provide a spacing betweenthe electrode component 114 and the first force sensor electrode 106.Any type of suitable material may be used to form the spacing layer 130,and any type of attachment mechanism may be used to physically couplethe spacing layer 130 to the first substrate 102 and second substrate110. In one embodiment, a thickness of the spacing layer 130 is between1/10^(th) and 1 millimeters. In another embodiment, the spacing layer130 comprises a double sided adhesive configured to physically couplethe first substrate 102 and second substrate 110.

Also in the illustrated embodiment, the input device 100 also includes acasing 120. The casing 120 includes force transmission element 122 thatis configured to transmit force to the electrode component 114.Specifically, the force transmission element 122 is physically coupledto the electrode component 114 such that when an input object (such as afinger) applies force, the force transmission element 122 causes theelectrode component 114 to bias relative to the first force electrode106, thus changing the variable capacitance. A measurement of the changevariable capacitance can be used to determine force informationregarding the force biasing the force transmission element 122.

An example of such force biasing is illustrated in FIG. 1C. Asillustrated in FIG. 1C, an increase in the force biasing the inputdevice 100 (as represented by arrow 120) causes the force transmissionelement 122 to transmit force to the electrode component 114, causingthe electrode component 114 to move relative to the first forceelectrode 106. As the distance between the electrode component 114 andthe first force electrode 106 changes, the variable capacitance, definedat least in part by electrode component 114 and first force electrode106, changes. A measurement of the variable capacitance betweenelectrodes can thus be used to determine force information for theobject providing the biasing force.

In the illustrated embodiment, the second substrate 110 comprises aconductive layer, where the second substrate is patterned to define thespring feature 112 and electrode component 114. This is best illustratedin FIG. 1B, where it can be seen that the spring features 112 and theelectrode components 114 are defined by patterning to remove selectedportions of material from the second substrate. Such a patterning of thesecond substrate may be performed using any suitable technique,including laser cutting, chemical etching, lithographic techniques,stamping, etc. Using such techniques may improve ease of devicemanufacturing and thus reduce cost and complexity.

In some embodiments the second substrate 110 may comprise a “stiffener”layer used to provide increased rigidity to the input device while atthe same time having desirable material properties in order tofacilitate consistent and repeatable movement of the electrode componentrelative to the first substrate. For example, stainless steel, berylliumcopper, phosphor bronze, and the like may be used as the “stiffener”layer material for the second substrate 110. In some embodiments, thesecond substrate 110 comprises a non-conductive material where theelectrode components 114 are formed with conductive material (eitherintegrally or disposed onto the second substrate).

Turning now to FIGS. 2A-2B, a cross-sectional and partial top view of aninput device 200 is illustrated. This embodiment differs from thatillustrated in FIG. 1 in that it includes two force sensors, with eachforce sensor using a transmitter force sensor electrode and a receiverforce sensor electrode. The input device 200 includes a first substrate202 with proximity sensor electrodes 204. Also disposed on the firstsubstrate 202 are transmitter force sensor electrodes 206 and receiverforce sensor electrodes 207. A second substrate 210 is physicallycoupled to the first substrate 202, where the second substrate comprisesspring features 212 and electrode components 214. The electrodecomponents 214 are arranged to at least partially overlap a transmitterforce sensor electrode 206 and a receiver force sensor electrode 207 todefine a variable capacitance between the transmitter force sensorelectrode 206, receiver force sensor electrode 207 and electrodecomponent 214. The spring features 212 are configured to facilitatedeflection of their respective electrode components 214 relative to thetransmitter force sensor electrode 206 and receiver force sensorelectrode 207 to change the variable capacitance. A measure of thevariable capacitance may be calculated and used to determine forceinformation regarding the force biasing the input device.

In the illustrated embodiment the input device 200 also includes aspacing layer 230, where the spacing layer 230 is pattered to defineopenings 232 such that the spacing layer does not overlap at least aportion of the transmitter force sensor electrode 206 and receiver forcesensor electrode 207 and to provide a spacing between the electrodecomponent 214 and the transmitter force sensor electrode 206 andreceiver force sensor electrode 207.

Also in this illustrated embodiment the second substrate is furtherpatterned to define an attachment feature 218. In this illustratedembodiment, the attachment feature 218 in the second substrate 210 isdefined in part by a slot 216 formed in the second substrate.Specifically, the slot 216 forms an attachment feature 218 thatcomprises a relatively thin piece of material such that the attachmentfeature is configured to deform elastically in response to a forceapplied to the first substrate.

Also in the illustrated embodiment, the input device 200 also includes acasing 220. The casing 220 includes force transmission elements 222 thatare configured to transmit force to the electrode components 214.Specifically, each force transmission element 222 is physically coupledto a corresponding electrode component 214 such that when an inputobject (such as a finger) applies force, the force transmission element222 causes the electrode component 214 to bias relative to thetransmitter electrode 206 and receiver electrode 208, thus changing thevariable capacitance. A measurement of the change variable capacitancecan be used to determine force information regarding the force biasingthe force transmission element 222. In the illustrated embodiment, thetransmission elements 222 are shown to be integrally formed with thecasing 220. In other embodiments, the transmission elements 222 may benon-integral features which are disposed between the casing 222 and thesecond substrate 210 which are configured to bias the electrodecomponent 214 in response to a force applied by an input object.

In this embodiment the casing 220 also comprises a mating feature 224.The mating feature 214 is configured to be coupled to the attachmentfeature 218 of the second substrate 210. For example, using any suitableattachment technique, such as welding, soldering, adhesives and thelike.

In one embodiment, the mating feature 224 and the force transmissionelement 222 are dimensioned such that the force transmission element 222applies a force to the electrode component when the casing 220 isphysically coupled to the second substrate 210 via mating features 224.

Specifically, in one particular embodiment these attachment features 218are configured to operate as “spring beams” that, when attached to themating features 224 of the casing 220 attach the second substrate 210(and any other physically coupled substrates) to the casing 220.Additionally, without requiring additional elements, such an attachmentmechanism provides “hold down” springs of the input device relative tothe casing. In these and other embodiments the casing 220 may be anintegral part of an electronic device (e.g. a palm rest) or furthercoupled to a base substrate of the electronic device.

In some embodiments the attachment features 218 may be spot welded tomating features 224 in the casing 220, with the features configured soas to slightly pre-load the “spring beams” once welded. As a result,when no force is imparted by an input object, the transmission elements222 are pulled to be in contact with the electrode components 214.Furthermore, any force imparted by an input object will bias theelectrode components 214 further towards the force sensor electrodes.

In FIG. 2B, an example of such a welding attachment is shown at points260. Specifically, the four points 260 show example locations where theattachment features 218 may be welded or otherwise attached to themating features 224. In this embodiment the attachment points arelocated at a midpoint of the “spring beam”, and thus may be used toprovide an effective pre-load on the spring beams. However, as will beshown later in FIG. 5 various other combinations of beam shapes andattachment locations can be used depending on the acceptable shear ofthe substrate, amount of deflection desired, etc.

It should be noted that when so provided, the use of such an attachmentfeature and mating feature may reduce the X/Y/Z form-factor that isrequired. Additionally, such a design may simplify assembly, while notincreasing height. Finally, it should be noted that the attachmentfeatures 218 may be formed in other portions of the second substrate210. Such an example will be shown in FIG. 5 below. Finally, alternateattachment methods, other than welds, can be employed to attach theinput device to the casing. Examples are metal crimps, screws, rivets,etc.

Again, in the illustrated embodiment the second substrate 210 comprisesa conductive layer, where the conductive layer is patterned to definethe spring features 212, the electrode components 214, and theattachment features 218. This is best illustrated in FIG. 2B, where atop view of the second substrate 210 shows that the spring features 212,the electrode components 214 and the attachment features 218 are definedby patterning to remove selected portions of material from theconductive layer. Such a patterning of the conductive layer may beperformed using any suitable technique, including laser cutting,chemical etching, lithographic techniques, stamping, etc. Using suchtechniques may improve ease of device manufacturing and thus reduce costand complexity.

As noted above, FIGS. 1 and 2 illustrate two examples of a secondsubstrate that comprises a patterned conductive layer, where the secondsubstrate is patterned to define spring features, electrode components,and in the case of FIG. 2, attachment features. However, it should benoted that these are merely examples of how such a second substrate maybe patterned, and that the resulting spring features, electrodecomponents, and attachment features could be configured in a variety ofdifferent ways.

Turning now to FIG. 3, a top view of another example second substrate310 is illustrated. Again, the patterned second substrate 310 comprisesspring features 312 and electrode components 314. The electrodecomponents 314 are arranged such that, when assembled, they at leastpartially overlap one or more force electrodes (not shown in this FIG)to define a variable capacitance. The spring features 312 are configuredto facilitate deflection of their respective electrode components 314relative to these force electrodes to change the variable capacitance.And again, a measure of the variable capacitance may be calculated andused to determine force information regarding the force biasing theinput device.

In the example embodiment of FIG. 3, the conductive layer is patternedsuch that four electrode components 314 are arranged about the perimeterof the second substrate 310. Furthermore, each electrode component 314differs from those in FIGS. 1 and 2 in that they are coupled to only twospring features 312, and at only one side of the electrode component314. Again, the spring features 312 and electrode component 314 may bedefined by patterning to remove selected portions of material from thesecond substrate.

Turning now to FIG. 4, a top view of another example second substrate410 is illustrated. In this embodiment the patterned second substrate410 again comprises spring features 412 and electrode components 414.The electrode components 414 are arranged such that, when assembled,they at least partially overlap one or more force electrodes to define avariable capacitance. The spring features 412 are configured tofacilitate deflection of their respective electrode components 414relative to these force electrodes to change the variable capacitance.In the example embodiment of FIG. 4, the conductive layer is patternedsuch that six electrode components 414 are arranged about the perimeterof the second substrate 410. Furthermore, each electrode component 414differs from those in previous embodiments in that it is coupled to onlyone spring feature 412. Again, the spring features 412 and electrodecomponent 414 may be defined by patterning to remove selected portionsof material from the conductive layer, using any suitable patterningtechnique.

Also illustrated in FIG. 4 is a component zone 450. In general, thecomponent zone 450 may be defined by patterning to remove selectedportions of material from the second substrate 410. The component zone450 is an area which may overlap one or more processing elements 452which may be located on the first substrate (not shown in this figure).These processing elements 452 may include portions of a suitableprocessing system, such as those described below with reference to FIG.7.

As has been shown in FIGS. 3-4, a variety of electrode component andspring feature patterns are possible. In some embodiments, at leastthree electrode components are patterned in the second substrate to format least three variable capacitances representative of a force appliedto the input surface of the input device. As will be described furtherbelow, the at least three variable capacitances may be calculated andused to determine force information regarding a force applied to theinput surface.

Turning now to FIG. 5, a top view of another exemplary second substrate510 is illustrated. In this embodiment the patterned second substrate510 comprises spring features 512 and one electrode component 514. Inthis illustrated embodiment, the single electrode component is arrangedat the center of the device. Again, the electrode component 514 would bepositioned such that, when assembled, it at least partially overlaps oneor more force electrodes on the first substrate to define a variablecapacitance. In this illustrated embodiment, four spring features 512are coupled to the single electrode component 514. Again, the springfeatures 512 and electrode component 514 may be defined by patterning toremove selected portions of material from the conductive layer, usingany suitable patterning technique.

Also in this illustrated embodiment the second substrate 510 is furtherpatterned to define four attachment features 518. In this illustratedembodiment the four attachment features 518 are arranged in proximity tothe four edges of the second substrate. This allows the second substrateto be reliably attached to a casing using the four attachment features518. Furthermore, each of the attachment features 518 allows the secondsubstrate to move in response to force applied by an input object.Specifically, by bonding the four attachment features 518 to a casing,the sensor device can be made responsive to force applied and allowed tomove. Furthermore, by dimensioning such features appropriately, adesired preload amount of force may be applied by the transmissionelements on to the electrode components.

In this illustrated embodiment, the attachment features 518 are eachdefined in part by a slot 516 formed in the second substrate.Specifically, the slot 516 forms an attachment feature 518 thatcomprises a relatively thin piece of material such that the attachmentfeature is configured deform in response to a force applied to the firstsubstrate.

As described above, in some embodiments the attachment features 518 maybe spot welded to mating features on a casing or other suitableconnection points. In FIG. 5 examples of such welding attachment isshown at points 560. Specifically, the points 560 show example locationswhere the attachment features 518 may be welded or otherwise attached tocorresponding mating features.

Turning now to FIG. 6, a top view of another example second substrate610 is illustrated. In this embodiment the patterned second substrate610 comprises spring features 612 and electrode components 614 for threedifferent force sensors. In this illustrated embodiment, the electrodecomponents 614 are arranged near the edges of the device. Again, theelectrode component 614 would be positioned such that, when assembled,it at least partially overlaps one or more force electrodes on the firstsubstrate to define variable capacitances. Again, the spring features612 and electrode component 614 may be defined by patterning to removeselected portions of material from the conductive layer, using anysuitable patterning technique.

Also in this illustrated embodiment the second substrate 610 is furtherpatterned to define three attachment features 618. In this illustratedembodiment two of attachment features 618 are arranged in proximity totwo of the corners, and the other attachment feature 618 is near an edgeof the second substrate. Again, these are examples of attachmentfeatures that can be provided to allow the second substrate to move inresponse to force applied by an input object. Specifically, by bondingthe attachment features 618 to a casing, the sensor device can be maderesponsive to force applied and allowed to move. Furthermore, bydimensioning such features appropriately, a desired preload amount offorce may be applied by the transmission elements on to the electrodecomponents.

In this illustrated embodiment, the attachment features 618 are eachdefined in part by one or more slots 616 formed in the second substrate.Specifically, the slots 616 define attachment features 618 that eachcomprises a relatively thin piece of material such that the attachmentfeature is configured deform in response to a force applied to the firstsubstrate.

As described above, in some embodiments the attachment features 618 maybe spot welded to mating features on a casing or other suitableconnection points. In FIG. 6 examples of such welding attachment isshown at points 660. Specifically, the points 660 show example locationswhere the attachment features 618 may be welded or otherwise attached tocorresponding mating features.

In some embodiments a processing system is communicatively coupled tothe force sensor electrodes (including transmitter and receiver forcesensor electrodes) and is configured to determine a capacitance value ofthe variable capacitance and to determine force information from thecapacitance value. In other embodiments the processing system is furthercommunicatively coupled to the proximity sensor electrodes and isconfigured to determine positional information for objects that are in asensing region using the proximity sensor electrodes. Theseimplementations offer potential advantages of sharing components betweenthe proximity sensor and the force sensor in the input device. Statedanother way, these implementations allow force sensing to be added to aproximity sensor with relatively low additional cost and complexity.

Turning now to FIG. 7, a block diagram illustrates an input device 716that combines a proximity sensor with a plurality of force sensors. Theinput device 716 uses both the proximity sensor and the force sensors toprovide an interface for the electronic system. The input device 716 hasa processing system 719, an input surface 721, sensing region 718 andthree force sensors 720 implemented proximate the sensing region 718. Aswill be described in greater detail below, each of the force sensors 720may be implemented with any of the various embodiments of force sensinginput devices described above and below, and thus may be configured toprovide a variety of force sensing. Furthermore, it should be noted thatone or more force sensors may be provided inside or outside theperimeter of the input surface 721. Not shown in FIG. 7 is an array ofsensing electrodes that are adapted to capacitively sense objects in thesensing region 718.

The input device 716 is adapted to provide user interface functionalityby facilitating data entry responsive to the position of sensed objectsand the force applied by such objects. Specifically, the processingsystem 719 is configured to determine positional information for objectssensed by a sensor in the sensing region 718. This positionalinformation can then be used by the system 700 to provide a wide rangeof user interface functionality. Furthermore, the processing system 719is configured to determine force information for objects from measuresof force determined by the force sensors 720. This force information canthen also be used by the system 700 to provide a wide range of userinterface functionality. For example, by providing different userinterface functions in response to different levels of applied force byobjects in the sensing region.

Force information for input objects may be determined by a variety ofdifferent mathematical techniques. An input device may be provided withN force sensors, each providing a force measurement F_(i). As describedabove, the input device is configured to determine positionalinformation for multiple objects using a sensor, such as a capacitiveproximity sensor. In this example, the position of M objects isexpressed using coordinates (x_(j), y_(j)). When the j^(th) objectapplies a force G_(j) at a location (x_(j), y_(j)), the response of thei^(th) force sensor can be modeled as h_(i)(x_(j), y_(j))·G_(j) whereh_(i) is a function of position that may either be derived from theinput device mechanical design or inferred from calibration data.Assuming that the response of the system to multiple forces is additive,the force measurement at each force sensor can be expressed as:

$F_{i} = {\sum\limits_{j}^{M}{{h_{i}\left( {x_{j},y_{j}} \right)} \cdot G_{j}}}$

Or in matrix notation,

f=H(x,y)·g

To reconstruct the finger forces g from the observations f (and theobserved positions x and y) the equation is inverted. In general, thenumber of fingers is not equal to the number of sensors (M≠N) and theresponses are not linearly independent (H is not invertible). A varietyof regularization techniques can be applied to solve this problem. Inone embodiment, a Tikhonov regularization is used to reconstruct thefinger forces g, such that:

ĝ=(H ^(T) ·H+α ² I)⁻¹ ·H ^(T) ·f

where α>0 is the Tikhonov factor. This is defined for any number andarrangement of fingers and sensors (i.e. for all M, N and H). Forappropriate values of α it is close to the true inverse if the trueinverse exists. When the inverse is not defined (e.g., the system isover- or under-constrained) the estimate remains consistent with theobservations, stable, and bounded.

The estimate ĝ minimizes the sum of the squared error and the norm ofthe solution vector

ĝ=arg min(∥H(x,y)·g−f∥ ²+α² ∥g∥ ²)

In the limit α→0 this approaches the least squares solution (thepseudo-inverse). For α≠0 we take into consideration the magnitude of thesolution vector as well as the goodness of fit, which stabilizes theestimate when (H^(T)·H)⁻¹ would otherwise become ill-conditioned.

The Tikhonov regularization can be interpreted as a Bayesian statisticalprior on the size of finger forces we anticipate. This interpretationcan motivate a choice of α as the inverse of the expected variance offinger forces. More generally, if additional information about theforces is available (such as the reconstructed forces at a previoustime, or a low force suggested by a small contact area), it cannaturally be incorporated into the Tikhonov method by replacing thescalar α with a matrix T describing the expected (co)variance of thefinger forces.

In embodiments comprising a rigid sensor that is mounted on a system ofideal springs, the response functions will be linear:

h _(i)(x _(j) ,y _(j))=k _(ix) ·x _(j) +k _(iy) ·y _(j) +k _(i0)

H(x,y)=K·[xy1]^(T)

In embodiments comprising non-rigid/non-ideal systems, the responsefunctions could be fitted to observations using as a combination of Lbasis functions (such as a polynomial or Fourier basis), such that

${h_{i}\left( {x_{j},y_{j}} \right)} = {\sum\limits_{k = 1}^{L}{c_{ki} \cdot {b_{k}\left( {x_{j},y_{j}} \right)}}}$

Such systems can still use the Tikhonov estimator, which depends only onlinearity with respect to applied force, and not on linearity withrespect to finger position.

In one embodiment, an input device comprising three force sensorsmounted at coordinates (−0.5, −0.5), (+0.5, −0.5), (0, 0), as such:

h ₀(x,y)=−x−y

h ₁(x,y)=+x−y

h ₂(x,y)=1+2y

This system can accurately reconstruct the forces of one finger, two(non-co-located) fingers and of three non-co-linear fingers. For threefingers that lie on a straight line or four or more fingers, the systemis under-determined; many possible finger forces g are consistent withthe observation f. In one embodiment, the regularization chooses areconstruction ĝ that requires the least applied force.

For example, when three fingers are evenly spaced along the line, theobservation is unable to distinguish between linear combinations of thevectors g=(3, 0, 3) and g=(0, 6, 0). In this situation, thereconstruction will propose g≈(2, 2, 2).

In another embodiment, an input device comprises four sensors mounted atthe corner coordinates (±0.5,±0.5), as such:

h _(i)(x,y)=0.25±x±y

In some embodiments, the assumption of rigidity renders the observationby the fourth sensor redundant, so this system has the samereconstruction capabilities as the three sensor system. Redundantsensors can have other advantages, such as robustness against failure ofone or more sensors.

In some embodiments, a not-rigid input surface results in non-linearresponse functions. In one example, a non-rigid system with four sensorsat the corner coordinates (±0.5,±0.5) comprises the response functions

h _(i)(x,y)=(0.5±x)(0.5±y)

The presence of an x·y term corresponds to saddle-shaped bending of thesurface. This bending allows this system to measure four independentvalues. The system can accurately reconstruct one and two(non-co-located) fingers, and most spatial configurations of three andfour fingers. Regularization provides acceptable estimates for theremaining configurations.

It should be noted that the above described technique is just oneexample of the type of techniques that can be used to determine forinformation. For example, other techniques that may be adapted for usein determining force information are described in U.S. PatentPublication No. US-2011-0141053-A1, entitled “SYSTEM AND METHOD FORMEASURING INDIVIDUAL FORCE IN MULTI-OBJECT SENSING”, which isincorporated herein by reference.

The input device 716 is sensitive to input by one or more input objects(e.g. fingers, styli, etc.), such as the position of an input object 714within the sensing region 718. Sensing region 718 encompasses any spaceabove, around, in and/or near the input device 716 in which the inputdevice 716 is able to detect user input (e.g., user input provided byone or more input objects 714). The sizes, shapes, and locations ofparticular sensing regions may vary widely from embodiment toembodiment. In some embodiments, the sensing region 718 extends from asurface of the input device 714 in one or more directions into spaceuntil signal-to-noise ratios prevent sufficiently accurate objectdetection. The distance to which this sensing region 718 extends in aparticular direction, in various embodiments, may be on the order ofless than a millimeter, millimeters, centimeters, or more, and may varysignificantly with the type of sensing technology used and the accuracydesired. Thus, some embodiments sense input that comprises no contactwith any surfaces of the input device 714, contact with an input surface(e.g. a touch surface) of the input device 714, contact with an inputsurface of the input device 714 coupled with some amount of appliedforce or pressure, and/or a combination thereof. In various embodiments,input surfaces may be provided by surfaces of casings within which thesensor electrodes reside, by face sheets applied over the sensorelectrodes or any casings, etc.

The input device 714 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 718.The input device 714 comprises one or more sensing elements fordetecting user input. As several non-limiting examples, the input device714 may use capacitive, elastive, resistive, inductive, magnetic,acoustic, ultrasonic, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In some resistive implementations of the input device 714, a flexibleand conductive first layer is separated by one or more spacer elementsfrom a conductive second layer. During operation, one or more voltagegradients are created across the layers. Pressing the flexible firstlayer may deflect it sufficiently to create electrical contact betweenthe layers, resulting in voltage outputs reflective of the point(s) ofcontact between the layers. These voltage outputs may be used todetermine positional information.

In some inductive implementations of the input device 714, one or moresensing elements pick up loop currents induced by a resonating coil orpair of coils. Some combination of the magnitude, phase, and frequencyof the currents may then be used to determine positional information.

In some capacitive implementations of the input device 714, voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes. Somecapacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g. system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects.

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a transcapacitive sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitters”) and one ormore receiver sensor electrodes (also “receiver electrodes” or“receivers”). Transmitter sensor electrodes may be modulated relative toa reference voltage (e.g., system ground) to transmit transmittersignals. Receiver sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. A resulting signal may comprise effect(s) corresponding to oneor more transmitter signals, and/or to one or more sources ofenvironmental interference (e.g. other electromagnetic signals). Sensorelectrodes may be dedicated transmitters or receivers, or may beconfigured to both transmit and receive.

In FIG. 7, a processing system 719 is shown as part of the input device716. The processing system 719 is configured to operate the hardware ofthe input device 716 to detect input in the sensing region 718. Theprocessing system 719 comprises parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. Forexample, a processing system for a mutual capacitance sensor device maycomprise transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes). In some embodiments,the processing system 719 also comprises electronically-readableinstructions, such as firmware code, software code, and/or the like. Insome embodiments, components composing the processing system 719 arelocated together, such as near sensing element(s) of the input device716. In other embodiments, components of processing system 719 arephysically separate with one or more components close to sensingelement(s) of input device 716, and one or more components elsewhere.For example, the input device 716 may be a peripheral coupled to adesktop computer, and the processing system 719 may comprise softwareconfigured to run on a central processing unit of the desktop computerand one or more ICs (perhaps with associated firmware) separate from thecentral processing unit. As another example, the input device 716 may bephysically integrated in a phone, and the processing system 719 maycomprise circuits and firmware that are part of a main processor of thephone. In some embodiments, the processing system 719 is dedicated toimplementing the input device 716. In other embodiments, the processingsystem 719 also performs other functions, such as operating displayscreens, driving haptic actuators, etc.

The processing system 719 may be implemented as a set of modules thathandle different functions of the processing system 719. Each module maycomprise circuitry that is a part of the processing system 719,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes and display screens, data processing modules for processingdata such as sensor signals and positional information, and reportingmodules for reporting information. Further example modules includesensor operation modules configured to operate sensing element(s) todetect input, identification modules configured to identify gesturessuch as mode changing gestures, and mode changing modules for changingoperation modes.

In some embodiments, the processing system 719 responds to user input(or lack of user input) in the sensing region 718 directly by causingone or more actions. Example actions include changing operation modes,as well as GUI actions such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 719 provides information about the input (or lack of input) tosome part of the electronic system (e.g. to a central processing systemof the electronic system that is separate from the processing system719, if such a separate central processing system exists). In someembodiments, some part of the electronic system processes informationreceived from the processing system 719 to act on user input, such as tofacilitate a full range of actions, including mode changing actions andGUI actions.

For example, in some embodiments, the processing system 719 operates thesensing element(s) of the input device 716 to produce electrical signalsindicative of input (or lack of input) in the sensing region 718. Theprocessing system 719 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system. For example, the processing system 719 may digitizeanalog electrical signals obtained from the sensor electrodes. Asanother example, the processing system 719 may perform filtering orother signal conditioning. As yet another example, the processing system719 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 719 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

Likewise, the term “force information” as used herein is intended tobroadly encompass force information regardless of format. For example,the force information can be provided for each object as a vector orscalar quantity. As another example, the force information can beprovided as an indication that determined force has or has not crossed athreshold amount. As other examples, the force information can alsoinclude time history components used for gesture recognition. As will bedescribed in greater detail below, positional information and forceinformation from the processing systems may be used to facilitate a fullrange of interface inputs, including use of the proximity sensor deviceas a pointing device for selection, cursor control, scrolling, and otherfunctions,

In some embodiments, the input device 716 is implemented with additionalinput components that are operated by the processing system 719 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 718, orsome other functionality.

In some embodiments, the input device 716 comprises a touch screeninterface, and the sensing region 718 overlaps at least part of anactive area of a display screen. For example, the input device 716 maycomprise substantially transparent sensor electrodes overlaying thedisplay screen and provide a touch screen interface for the associatedelectronic system. The display screen may be any type of dynamic displaycapable of displaying a visual interface to a user, and may include anytype of light emitting diode (LED), organic LED (OLED), cathode ray tube(CRT), liquid crystal display (LCD), plasma, electroluminescence (EL),or other display technology. The input device 716 and the display screenmay share physical elements. For example, some embodiments may utilizesome of the same electrical components for displaying and sensing. Asanother example, the display screen may be operated in part or in totalby the processing system 719.

It should be understood that while many embodiments of the invention aredescribed in the context of a fully functioning apparatus, themechanisms of the present invention are capable of being distributed asa program product (e.g., software) in a variety of forms. For example,the mechanisms of the present invention may be implemented anddistributed as a software program on information bearing media that arereadable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 719). Additionally, the embodiments ofthe present invention apply equally regardless of the particular type ofmedium used to carry out the distribution. Examples of non-transitory,electronically readable media include various discs, memory sticks,memory cards, memory modules, and the like. Electronically readablemedia may be based on flash, optical, magnetic, holographic, or anyother storage technology.

As noted above, the input device 716 may be implemented with a varietyof different types and arrangements of capacitive sensing electrodes. Toname several examples, the capacitive sensing device may be implementedwith electrode arrays that are formed on multiple substrate layers,including parts of the same layers used to form the force sensors. Asone specific embodiment, electrodes for sensing in one direction (e.g.,the “X” direction) may formed on a first layer (e.g., on a first side ofthe first substrates of FIGS. 1-2, or any other suitable substrate),while the electrodes for sensing in a second direction (e.g., the “Y”direction are formed on a second layer (e.g., on another side of thefirst substrate or any other suitable substrate).

In other embodiments, the electrodes for both the X and Y sensing may beformed on the same layer, with that same layer comprising any of thesubstrates described in FIGS. 1-2. In yet other embodiments, theelectrodes may be arranged for sensing in only one direction, e.g., ineither the X or the Y direction. In still another embodiment, theelectrodes may be arranged to provide positional information in polarcoordinates, such as “r” and “θ” as one example. In these embodimentsthe electrodes themselves are commonly arranged in a circle or otherlooped shape to provide “θ”, with the shapes of individual electrodesused to provide “r”. Also, a variety of different electrode shapes maybe used, including electrodes shaped as thin lines, rectangles,diamonds, wedge, etc. Finally, a variety of conductive materials andfabrication techniques may be used to form the electrodes. As oneexample, the electrodes are formed by the deposition and etching ofcopper or ITO on a substrate.

To facilitate operation of the force sensor, it is generally desirableto provide an appropriate ohmic coupling between the processing systemand patterned conductive layer—more specifically, the electrodecomponents formed in the patterned conductive layer. Such a connectionmay be provided in a variety of ways. Turning now to FIG. 8, across-sectional view of an input device 800 is illustrated. The inputdevice 800 again includes a first substrate 802 with proximity sensorelectrodes 804 and at least a first force sensor electrode 806 disposedon the first substrate. A second substrate 810 is physically coupled tothe first substrate 802, where the second substrate comprises at leastone spring feature 812 and at least one electrode component 814. Theelectrode component 814 at least partially overlaps the first forcesensor electrode 806 to define a variable capacitance between the firstforce sensor electrode 806 and the electrode component. The input device100 also includes a spacing layer 830, where the spacing layer 830 ispattered to define an opening 832 such that the spacing layer 830 doesnot overlap at least a portion of the electrode component 814 and toprovide a spacing between the electrode component 814 and the firstforce sensor electrode 806. Also in the illustrated embodiment, theinput device 800 also includes a casing 820. The casing 820 includesforce transmission element 822 that is configured to transmit force tothe electrode component 814.

Also shown in the embodiment of FIG. 8 is a conductive path 850 includedin the spacing layer 830. The conductive path 850 is configured tooverlap a conductive pad 852 on the first substrate and provide aconductive path between a conductive layer of the second substrate 810and the first substrate 802. Using the conductive path 850, the secondsubstrate 810 may be ohmically coupled to the processing system tofacilitate force sensing. As such, any suitable conductive materials orstructure such as conductive gaskets, glues, or foams may be used toohmically couple the second substrate 810 to the processing system.

The embodiments and examples set forth herein were presented in order tobest explain the present invention and its particular application and tothereby enable those skilled in the art to make and use the invention.However, those skilled in the art will recognize that the foregoingdescription and examples have been presented for the purposes ofillustration and example only. The description as set forth is notintended to be exhaustive or to limit the invention to the precise formdisclosed.

What is claimed is:
 1. An input device comprising: a first substrate;proximity sensor electrodes disposed on the first substrate, theproximity sensor electrodes configured to detect objects in a sensingregion; a first force sensor electrode disposed on the first substrate;and a second substrate physically coupled to the first substrate, thesecond substrate comprising a spring feature and an electrode component,wherein the electrode component at least partially overlaps the firstforce sensor electrode to define a variable capacitance between thefirst force sensor electrode and the electrode component, and whereinthe spring feature is configured to facilitate deflection of theelectrode component relative to the first force sensor electrode tochange the variable capacitance.
 2. The input device of claim 1 whereinthe second substrate comprises a conductive layer, and wherein theconductive layer is patterned to define the spring feature and theelectrode component.
 3. The input device of claim 1 wherein theproximity sensor electrodes and the first force sensor electrode aredisposed on different layers of the first substrate.
 4. The input deviceof claim 1 wherein the second substrate is physically coupled to thefirst substrate with a spacing layer, wherein the spacing layer ispatterned to not overlap at least a portion of the electrode componentand provide a spacing between the electrode component and the firstforce sensor electrode.
 5. The input device of claim 4 wherein thespacing layer comprises a conductive feature configured to ohmicallycouple the second substrate to a contact disposed on the firstsubstrate.
 6. The input device of claim 1 wherein the second substratefurther comprises an attachment feature, and wherein the attachmentfeature is defined in part by a slot formed in the second substrate,wherein the attachment feature is configured deform in response to aforce applied to the first substrate.
 7. The input device of claim 1further comprising a casing, wherein the casing comprises a forcetransmission element, the force transmission element configured tofacilitate deflection of the electrode component in response to forceapplied to the first substrate.
 8. The input device of claim 7 whereinthe casing further comprises an mating feature, the mating featureconfigured to be coupled to the attachment feature of the second layer,and wherein the mating feature and the force transmission element of thecasing are dimensioned such that the force transmission element appliesa force to the electrode component when the casing is physically coupledto the second substrate.
 9. The input device of claim 1 furthercomprising a processing system, the processing system communicativelycoupled to the proximity sensor electrodes, the electrode component andthe first force sensor electrode, wherein the processing system isconfigured to determine a capacitance value of the variable capacitanceand to determine force information from the capacitance value.
 10. Theinput device of claim 9 further comprising a second force sensorelectrode disposed on the first substrate, and wherein the electrodecomponent of the second substrate at least partially overlaps the secondforce sensor electrode, and wherein the first force sensor electrodecomprises a transmitter electrode and wherein the second force sensorelectrode comprises a receiver electrode.
 11. A method of forming aninput device comprising: providing a first substrate; disposing aplurality of sensor electrodes on the first substrate, the plurality ofsensor electrodes configured to detect objects in a sensing region;disposing a first force sensor electrode on the first substrate;patterning a second substrate to define a spring feature and anelectrode component in the second substrate, the spring featureconfigured to facilitate deflection of the electrode component; andphysically coupling the second substrate to the first substrate suchthat the electrode component at least partially overlaps the first forcesensor electrode to define a variable capacitance between the firstforce sensor electrode and the electrode component and such thatdeflection of the electrode component feature relative to the firstforce sensor electrode changes the variable capacitance.
 12. The methodof claim 11 wherein the second substrate comprises a metal layer, andwherein the metal layer is patterned by a technique selected from agroup consisting of laser cutting, stamping and chemical etching. 13.The method of claim 11 further comprising providing a spacing layerwherein the second substrate is physically coupled to the firstsubstrate with the spacing layer, wherein the spacing layer is patternedto not overlap at least a portion of the electrode component andprovides a spacing between the electrode component and the first forcesensor electrode.
 14. The method of claim 11 further comprisingpatterning a slot in the second substrate to define an attachmentfeature, wherein the feature is configured deform in response to a forceapplied to the first substrate.
 15. The method of claim 11 furthercomprising coupling a casing to the second substrate, wherein the casingcomprises a force transmission element, the force transmission elementconfigured to facilitate deflection of the electrode component inresponse to force applied to the first substrate.
 16. The method ofclaim 15 wherein the casing further comprises a mating feature, themating feature configured to be coupled to the attachment feature of thesecond substrate, and wherein the mating feature and the forcetransmission element of the casing are dimensioned such that the forcetransmission element applies a force to the electrode component when thecasing is physically coupled to the second substrate.
 17. An inputdevice comprising: a substrate; a plurality of proximity sensorelectrodes disposed on the substrate, the proximity sensor electrodesconfigured to detect objects in a sensing region; a transmitter forcesensor electrode and a receiver force sensor electrode disposed on thesubstrate; a conductive layer physically coupled to the first substrate,the conductive layer patterned to define at least one attachmentcomponent in the conductive layer, at least one spring feature in theconductive layer and at least one electrode component in the conductivelayer, wherein the electrode component at least partially overlaps thetransmitter force sensor electrode and the receiver sensor electrode todefine a variable capacitance between the transmitter force sensorelectrode, the receiver sensor electrode and the electrode component,and wherein the spring feature is configured to facilitate deflection ofthe electrode component relative to the transmitter force sensorelectrode and the receiver sensor electrode to change the variablecapacitance; and a casing, the casing comprising an mating element and aforce transmission element, the mating element configured to be coupledto the attachment component of the conductive layer, and wherein themating element and the force transmission element are dimensioned suchthat the force transmission element applies preload force to theelectrode component when the attachment element is coupled to theattachment component and such that the force transmission elementtransmits additional force to electrode component in response to forceapplied by a user.
 18. The input device of claim 17 further comprising aprocessing system communicatively coupled to the transmitter forcesensor electrode and the receiver force sensor electrode, the processingsystem configured to determine a capacitance value of the variablecapacitance and to determine force information from the capacitancevalue.
 19. The input device of claim 18 wherein the processing system isfurther communicatively coupled to the plurality of proximity sensorelectrodes, and wherein the processing system is further configured tooperate the plurality of proximity sensor electrodes to sense objects ina sensing region.
 20. The input device of claim 17 further comprising aslot in the conductive layer, wherein the slot defines at least in partthe attachment component, and wherein the attachment feature isconfigured deform in response to a force applied to the substrate.